1. Field of the Invention
The present invention relates generally to an air and moisture separator for a vacuum waste tank system.
2. Related Art
As typically know to most travelers, flushing an aircraft toilet results in the waste fluids and solids being “sucked” from the toilet bowl into a tank via a drain pipe. This fundamental process provides a system that is relatively simple, low in weight, and low in odor in comparison to other systems like a re-circulating toilet used in older aircraft. The principles of this system are based on the pressure differential between the cabin pressure inside the aircraft and the lower air pressure outside of the aircraft at flight altitude. When a patron flushes a toilet, a valve opens to the outside air creating a decrease in pressure or “vacuum” on the sewage waste system in comparison to the cabin pressure. This vacuum pulls the waste fluids and solids from the toilet bowl, through a drain line, and into a holding tank. When the aircraft is on the ground or at lower flight altitudes where this differential of pressures is less than optimal, a vacuum blower is used to boost the differential pressure to the necessary level for the waste system to function correctly.
The fundamental parts of this system comprise of a toilet bowl, a drain line to the holding tank, the holding (waste) tank, and air lines connecting the waste tank to the vacuum blower and the atmosphere outside the aircraft. The waste tank is a simple vacuum vessel used to retain the waste fluids and solids flushed down the toilet until the time the aircraft has landed and tank can be drained. The tank contains sensors, waste inlets and diverts, rinse system, drain, and air-water separator.
The sensors detect the level of the waste inside the tank determining how full the tank is. The sensors are mounted at a certain height along the inner face of the tank wall. They function by analyzing the height of the waste fluids and solids and creating an electronic signal. When the tank is full, the sensors will shut down power to the restrooms connected to it.
The waste inlets and diverts connect the drain line from the toilets to the waste tank. The inlets support the waste system in such a way that the vacuum pressure in the tank draws the waste matter from the toilet, through the drain pipe, through the inlets, and into the tank. The diverts work in conjunction with the inlets of the tank and are aligned with the inlets on the inside of the cap. These work to direct the flow of the waste matter that comes into the tank away from the sensors and air-water separator and reduce the splash of waste matter as it enters the tank. The intent of this is to reduce coating the sensor faces with a buildup of waste fluids and solids that can result in the sensors giving a false reading of a full tank and minimize the amount of fluids and solids impacting/clogging the air-water separator.
Rinse systems are installed into the waste tank in which clean water can be sprayed through the rinse system to clean out the inside of the waste tank during servicing. One of the primary aspects of the rinse system is to remove the liquid and solid waste buildup from the face of the sensors in order to ensure the sensors are providing accurate readings of the waste level in the tank.
The air-water separator, which typically sits at the top of the waste tank, connects the tank to air lines that run to the vacuum blower and the exterior of the aircraft. The separator filters out liquid and solid particulates entrained in the airflow which is generated by vacuum from the external pressure differential or the vacuum blower. It does this though the use of baffles and filtering materials which are typically assembled in a replaceable filter canister. One of the shortcomings of current separator designs is that due to most spatial requirements within the aircraft, the air-water separator is typically required to project downwardly into the tank. This in turn reduces the maximum fluid level within the tank thus diminishing the efficiency of the tank.
Secondly, concern exists about fine particulates bypassing the filter mesh, due to its larger pores, and adhering to the walls of piping and equipment downstream of the air-water separator. This can have adverse effects on the vacuum blowers which could result in ultimate failure and lost time and money in maintenance.
Various separators are shown in U.S. Pat. Nos. 6,206,943; 5,026,407; and 7,998,251.